Have you ever seen an external CPU connected to a laptop. I think this is a crappy question.
Why yes I have, but those plugged into an expansion port on the back of the laptop which had access to the buses and clocks. Modern laptops do not give you this access. Those "modules" also could have their own memory. The last time I saw one - the processor was a 486; to give an idea of how long ago this was, and it was so the user could run native windows OS and applications on their non-intel laptop. These were also fairly common as drop in cards for desktops for Apples and Amiga's iirc.